U.S. patent application number 12/065023 was filed with the patent office on 2008-10-02 for fuel injection system having reduced pollutant emissions.
Invention is credited to Holger Rapp, Udo Schulz.
Application Number | 20080236554 12/065023 |
Document ID | / |
Family ID | 37198811 |
Filed Date | 2008-10-02 |
United States Patent
Application |
20080236554 |
Kind Code |
A1 |
Rapp; Holger ; et
al. |
October 2, 2008 |
Fuel Injection System Having Reduced Pollutant Emissions
Abstract
A fuel injection system for an internal combustion engine is
proposed. The fuel injection system has a high pressure part and a
low pressure part. In the high pressure part, fuel is fed from at
least one high pressure accumulator/reservoir to at least one fuel
injector. In the low pressure part, the at least one fuel injector
is connected to at least one low pressure accumulator/reservoir,
wherein a pressure is maintained in the at least one low pressure
accumulator by at least one pressure holding valve. Furthermore,
the fuel injection system has at least one device for the
after-treatment of exhaust gases of the internal combustion engine
in an exhaust gas section. Furthermore, the fuel injection system
has at least one metering device for the metered introduction of
fuel into the exhaust gas section. Said at least one metering
device is connected hydraulically to the at least one low pressure
accumulator.
Inventors: |
Rapp; Holger; (Ditzingen,
DE) ; Schulz; Udo; (Vaihingen/Enz, DE) |
Correspondence
Address: |
RONALD E. GREIGG;GREIGG & GREIGG P.L.L.C.
1423 POWHATAN STREET, UNIT ONE
ALEXANDRIA
VA
22314
US
|
Family ID: |
37198811 |
Appl. No.: |
12/065023 |
Filed: |
July 21, 2006 |
PCT Filed: |
July 21, 2006 |
PCT NO: |
PCT/EP2006/064520 |
371 Date: |
February 27, 2008 |
Current U.S.
Class: |
123/672 ;
60/303 |
Current CPC
Class: |
Y02T 10/26 20130101;
F01N 3/2033 20130101; F01N 2610/03 20130101; F02M 37/0052 20130101;
F02M 55/002 20130101; F02M 63/0225 20130101; F01N 3/0253 20130101;
F01N 3/36 20130101; Y02T 10/12 20130101 |
Class at
Publication: |
123/672 ;
60/303 |
International
Class: |
F02D 41/00 20060101
F02D041/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 30, 2005 |
DE |
102005040918.0 |
Claims
1-11. (canceled)
12. A fuel injection system for an internal combustion engine,
comprising: a high-pressure part having at least one high-pressure
reservoir delivering fuel to at least one fuel injector; a
low-pressure part having at least one low-pressure reservoir in
communication with the at least one filet injector; at least one
pressure maintenance valve maintaining pressure in the at least one
low-pressure reservoir; at least one device for posttreatment of
exhaust gases of the engine, the posttreatment device disposed in
an exhaust system of the internal combustion engine; and at least
one metering device for metered introduction of fuel into the
exhaust system; wherein the at least one metering device is in
hydraulic communication with the at least one low-pressure
reservoir.
13. The fuel injection system according to claim 12, wherein the at
least one metering device has at least one metering valve.
14. The fuel injection system according to claim 12, wherein the at
least one metering device is disposed in an exhaust manifold of the
exhaust system.
15. The fuel injection system according to claim 13, wherein the at
least one metering device is disposed in an exhaust manifold of the
exhaust system.
16. The fuel injection system according to claim 12, wherein the at
least one pressure maintenance valve is embodied such that the
pressure that can be maintained in the at least one low-pressure
reservoir does not exceed a predetermined maximum pressure.
17. The fuel injection system according to claim 12, wherein the
pressure that can be maintained in the at least one low-pressure
pan is between 5 bar and 20 bar, preferably 10 bar.
18. The fuel injection system according to claim 13, wherein the
pressure that can be maintained in the at least one low-pressure
part is between 5 bar and 20 bar, preferably 10 bar.
19. The fuel injection system according to claim 14, wherein the
pressure that can be maintained in the at least one low-pressure
part is between 5 bar and 20 bar, preferably 10 bar.
20. The fuel injection system according to claim 12, wherein the at
least one low-pressure reservoir has a communication between the at
least one low-pressure reservoir and the at least one metering
device, and the at least one metering device has no additional
pump.
21. The fuel injection system according to claim 13, wherein the at
least one low-pressure reservoir has a communication between the at
least one low-pressure reservoir and the at least one metering
device, and the at least one metering device has no additional
pump.
22. The fuel injection system according to claim 17, wherein the at
least one low-pressure reservoir has a communication between the at
least one low-pressure reservoir and the at least one metering
device, and the at least one metering device has no additional
pump.
23. The fuel injection system according to claim 12, further
comprising a pressure measurement system for detecting the pressure
in the at least one low-pressure part.
24. The fuel injection system according to claim 13, further
comprising a pressure measurement system for detecting the pressure
in the at least one low-pressure part.
25. The fuel injection system according to claim 22, further
comprising a pressure measurement system for detecting the pressure
in the at least one low-pressure part.
26. The fuel injection system according to claim 12, further
comprising at least one control unit, the control unit being
equipped to control the at least one metering device, as a function
of the detected pressure in the at least one low-pressure part.
27. The fuel injection system according to claim 12, wherein the at
least one device for posttreatment of exhaust gases of the engine
is embodied by one of a filter and a catalytic converter.
28. The fuel injection system according to claim 22, wherein the at
least one device for posttreatment of exhaust gases of the engine
is embodied by one of a filter and a catalytic converter.
29. The fuel injection system according to claim 12, wherein the at
least one device for posttreatment of the exhaust gases has at
least one heating device.
30. The fuel injection system according to claim 22, wherein the at
least one device for posttreatment of the exhaust gases has at
least one heating device.
31. The fuel injection system according to claim 12, wherein the at
least one pressure maintenance valve has a throttle bore.
Description
[0001] The invention relates to a fuel injection system for
internal combustion engines, in particular for direct-injection
internal combustion engines, which compared to conventional fuel
injection systems has reduced pollutant emissions. Fuel injection
systems of this kind can be used particularly for internal
combustion engines in the automotive industry, in the field of
utility vehicles.
PRIOR ART
[0002] In internal combustion engine technology, direct-injection
internal combustion engines are being used increasingly,
particularly in the field of diesel engines. In them, fuel from a
fuel tank is fed via a high-pressure pump system into a
high-pressure reservoir (common rail), which in turn is in
communication with one or more fuel injectors for injecting the
fuel into the combustion chamber of the engine.
[0003] As exhaust gas standards become increasingly stringent and
given the constant attempt to reduce environmental pollution,
numerous systems for posttreating exhaust gases from these internal
combustion engines are already being used. Examples that can be
mentioned in particular are particle filters, catalytic converters,
or combinations of such systems. These systems for posttreating the
exhaust gases, however, are often linked with the disadvantage that
regular regeneration of the systems is necessary, in order to
remove particles, especially soot particles, that have collected in
these systems. This regeneration can be done for instance by means
of brief temperature elevations, in which particles in the exhaust
gas cleaning systems are oxidized and thus removed from the exhaust
gas cleaning systems. Typically, stored NOx is reduced by means of
uncombusted hydrocarbons.
[0004] A known method in the prior art for posttreating exhaust
gases is disclosed in German Patent Disclosure DE 198 30 275 A1.
This provides a device for posttreating exhaust gases, in the form
of a reducing catalytic converter for reducing NOx components of an
exhaust gas stream. Diesel fuel is used as the reducing agent;
through a special injection nozzle disposed in the exhaust gas
tube, it is introduced in such a way that it is aimed in a thin
stream at the opening of the outlet valve that opens after a cycle
of the engine. By "cracking" and evaporation, the fuel thus
introduced is prepared as a reducing agent for reducing the NOx
components of the exhaust gas that are stored in the reducing
catalytic converter.
[0005] The method disclosed in DE 198 30 275 A1 for reinforcing
exhaust gas preparation is one example of a so-called postinjection
method. Such injection concepts with postinjections to support
exhaust gas preparation and/or the regeneration of the systems for
exhaust gas preparation, however, have the disadvantage that the
postinjection must be controlled chronologically extremely
precisely. The postinjection is effected either through the fuel
injection valve itself or, as in the case of DE 198 30 275 A1,
through a special injection nozzle.
[0006] However, if the postinjection quantity is introduced into
the engine too soon, it already combusts in the engine, so that on
the one hand the exhaust gas temperature is affected in an unwanted
way, and on the other, the desired supporting and/or preparing
effect of the system is lost for the prose of exhaust gas
preparation. If an injection is too late, conversely, the desired
cracking effect does not ensue, and thus the postinjection quantity
strikes the cylinder wall, for instance, and rinses off the film of
lubricant located there and causes the lubricating oil to be
diluted with diesel fuel. Thus if injection is too early, the
exhaust gas is worsened, and if a postinjection is too late, there
is increased wear in the engine because of poorer lubrication. In
an extreme case, this latter factor can cause so-called "racing" of
the engine from uncontrolled combustion of lubricating oil
containing a large amount of diesel fuel.
[0007] A remedy to these problems could be provided by making the
postinjection not into the combustion chamber but rather directly
into the hot exhaust system of the engine. In such concepts, work
is done by way of a separate low-pressure injection valve preceded
by an electrically actuated metering pump. Such systems are also
known as HCI systems (for hydrocarbon injection). With such
engines, the possibility also exists of making do in the engine
control unit with single-bank injection stage concepts rather than
two-bank injection stage concepts, since the late postinjections
via the injectors into the engine are omitted. Thus the costs for
both electronics and materials are less, and a power loss of the
engine control unit is reduced. In addition, the quantity required
from the high-pressure pump is reduced, thus making it possible to
use smaller pumps as well, in particular single-plunger pumps. The
power losses from the requisite generation of high pressure are
accordingly less.
[0008] Nevertheless, such HCI systems have the disadvantage of
requiring complicated additional components. In particular, a
separate low-pressure injection valve preceded by an electrically
actuated metering pump is necessary. The use of such complicated
metering pumps with corresponding electrical control is a
particular factor making such HCI systems expensive in terms of
space and cost.
ADVANTAGES OF THE INVENTION
[0009] A fuel injection system is therefore proposed which
overcomes the disadvantages of the systems for supporting exhaust
gas preparation known from the prior art and that can be realized
in a simple way. A fundamental concept of the present invention is
to modify the concept, known from the HCI systems, such that the
use of a metering valve can be dispensed with. A fundamental idea
is to modify the low-pressure region, which is included anyway in
many internal combustion engines, in such a way that it serves at
the same time to subject the metering valve to pressure, as a
result of which the low-pressure pump can be omitted.
[0010] The fuel injection system has a high-pressure part and a
low-pressure part; in the high-pressure part, fuel from at least
one high-pressure reservoir can be delivered to at least one fuel
injector. In the low-pressure part, which may embodied in
particular as a leak fuel return, the at least one fuel injector is
in communication with at least one low-pressure region. For
instance, it may be a so-called "leak fuel rail".
[0011] A further fundamental concept of the invention is to provide
at least one pressure maintenance valve in the at least one
low-pressure reservoir. Low-pressure reservoirs with low-pressure
maintenance valves are known from the prior art, such as
International Patent Disclosure WO 2005/010351. These known systems
predominantly involve piezoelectric injectors with hydraulic
couplers for stroke boosting and temperature compensation, which to
refill the coupler require a pressure in the return branch of
approximately 10 bar. For reasons of cost and simplicity, this
pressure is generated by combining the leak fuel lines of the
injectors into a leak fuel rail, and the diverted quantity from the
injectors flowing out via this leak fuel rail is carried via a
mechanical pressure maintenance valve and dammed up there to a
pressure of approximately 10 bar.
[0012] One discovery of the present invention accordingly comprises
using this damming up of the pressure by the at least one pressure
maintenance valve simultaneously for building up a requisite
metering pressure and thus to replace a low-pressure pump for the
metering. Preferably, the at least one pressure maintenance valve
is embodied such that the pressure that can be maintained in the at
least one low-pressure reservoir does not exceed a predetermined
maximum pressure. Preferably, the pressure is set to between 5 bar
and 20 bar, and especially preferably to 10 bar.
[0013] The fuel injection system according to the invention
furthermore has a device for posttreating exhaust gases of the
engine in an exhaust system. Especially preferably, this device in
turn has a filter, in particular a particle filter, preferably an
NOx particle filter and/or a soot particle filter, and/or a
catalytic converter, in particular a storage catalytic converter,
preferably an NOx storage catalytic converter.
[0014] In addition, at least one metering device for metered
introduction of fuel into the exhaust system is provided in the
fuel injection system. This at least one metering device
communicates fluidically with the at least one low-pressure
reservoir, and preferably no additional low-pressure pump for
attaining a metering pressure is provided. The at least one
metering device preferably has at least one metering valve.
[0015] The at least one metering device can preferably be located
in an exhaust manifold of the exhaust system. This assures that
especially efficient atomization and distribution of the metered-in
fuel takes place in the exhaust system. Moreover, this arrangement
assures that safe, reliable cracking of the fuel, in particular
diesel fuel, takes place in the hot exhaust gas. The metered-in
fuel, as in the prior art, serves to regenerate the at least one
device for posttreating the exhaust gases and/or for reinforcing
the posttreatment. For instance, the metered-in fuel, by combustion
in the device for posttreating exhaust gases, can briefly assure a
temperature elevation there, and soot particles, for instance, are
burned off and eliminated in the form of carbon dioxide.
[0016] This combustion can additionally be reinforced by one or
more heating devices in the device for posttreating the exhaust
gases, which preferably cooperates with the metering in of fuel
into the exhaust system. Thus by means of this heating device, the
temperature can briefly be elevated, in order to reinforce the
reaction of the metered-in fuel with the contaminants.
[0017] In addition, the metered-in fuel can also act as a reducing
agent; preferably, cracking (for instance, thermally reinforced
cracking) of the metered-in fuel takes place, so as to make an
especially effective reducing agent available for reducing NOx, for
example. This process too can be additionally reinforced by means
of a heating device.
[0018] The injection of fuel into the exhaust system can be done
periodically for instance, such as once per cycle of the engine.
Alternatively or in addition, however, special injections may be
provided at predetermined or variable intervals, for instance every
10 km or every 1000 km, by means of which a special regeneration
process is initiated. For the permanent injection into the exhaust
system to reinforce the exhaust gas preparation on the one hand and
for a regeneration injection on the other, for example, different
injection quantities may be provided. This injection may for
instance be controlled by an engine control unit. It is also
possible for a plurality of injection sites to be provided, which
are employed for instance at different times and for different
purposes.
[0019] It is especially preferable if the at least one metering
device and the at least one low-pressure reservoir, fluidically
communicating with the at least one metering device, are adapted to
one another. This can be done for instance by providing a pressure
measurement system in the at least one low-pressure reservoir or
other component of the low-pressure part, for detecting the
pressure in the at least one low-pressure reservoir. Still other
measuring systems may be provided, such as temperature measuring
systems, which detect the fuel temperature in the at least one
low-pressure reservoir. The use of a pressure measurement system
has proved especially advantageous in collaboration with a further
advantageous feature of the invention in which the at least one
pressure maintenance valve has a throttle bore, and in particular
is embodied as a throttle bore.
[0020] The at least one metering device can be adapted to these
parameters of the fuel in the at least one low-pressure reservoir,
for which purpose a control unit (for instance the engine control
unit) can be used. Thus the at least one metering device can for
instance be controlled by the control unit as a function of the
detected pressure in the at least one low-pressure reservoir. In
particular, it is possible in this way for the metering duration,
such as the opening duration of a metering valve, to be adapted to
the pressure detected in the low-pressure reservoir. It can be
assured in this way that the injection quantity does not exceed
and/or fall short of predetermined tolerances. The metering can
also be done as a function of the fuel temperature; at elevated
fuel temperature, for instance (and thus at elevated reactivity of
the fuel), only a lesser fuel quantity can then be metered in. Once
again, this increases the efficiency of the fuel injection system
for preparing the exhaust gases.
[0021] The fuel injection system of the invention, in one of the
embodiments described above, has numerous advantages over
conventional fuel injection systems known from the prior art. In
particular, as already described above, it is possible to dispense
with the use of a low-pressure pump for metering fuel. As a result,
fewer assembly steps are needed, and the system can be designed in
a more space-saving, economical way. Numerous electrical or
electronic controls for the metering pump can also be dispensed
with. In this way, low-cost solutions are attainable even for
instance in piezoelectric common rail injection systems. Naturally,
the fuel injection system of the invention can additionally be
expanded with a low-pressure pump, but in the sense of the
invention this low-pressure pump can be smaller in size than in
conventional systems.
[0022] A further advantage of the system of the invention is that
the fuel, arriving from the tank initially via the high-pressure
reservoir, flows via throttles in the fuel injector before reaching
the low-pressure reservoir. In the process, this fuel warms up
considerably, typically by approximately 60.degree. C., and
consequently in the low-pressure reservoir it has a markedly
elevated temperature, compared to the tank and/or the high-pressure
reservoir. This has multiple advantages, depending on the field in
which it is employed.
[0023] If the injected fuel is used to reinforce the posttreatment
of the exhaust gases, for instance for reducing NOx, then the
elevated pressure of the injected fuel causes it to be more
reactive and/or more easily converted into reactive reduction
media. In the regeneration of devices for posttreating exhaust
gases as well, for instance in regeneration of soot particle
filters, the elevated temperature of the injected fuel is of
considerable advantage.
[0024] A further advantage of the system of the invention comprises
the homogeneity of the injected fuel in the exhaust system. Dips in
the pressure in the low-pressure reservoir from the postinjection
via the metering device are not to be expected in present internal
combustion engines, especially those with piezoelectric injectors,
since the return volumetric flow of fuel, returning from the fuel
injectors via the low-pressure reservoir, exceeds the quantity
required for the postinjection in every case. As described above,
depending on the control precision of the pressure maintenance
valve at the low-pressure reservoir, the pressure in the
low-pressure reservoir can optionally be detected by the engine
control unit in addition and used for calculating the triggering
duration of the metering device. In this way, the uniformity of the
postinjection is additionally enhanced.
DRAWING
[0025] The invention will be described in further detail below in
conjunction with the drawings.
[0026] Shown are:
[0027] FIG. 1, a fuel injection system of the invention without an
additional metering pump for postinjection of fuel.
EXEMPLARY EMBODIMENTS
[0028] In the sole drawing (FIG. 1), a fuel injection system of the
invention is shown in an especially preferred embodiment. This is a
so-called HCI system that is employed for regenerating a particle
filter.
[0029] The fuel injection system 110 has a bank (represented
symbolically) of fuel injectors 112, by means of which fuel can be
injected into combustion chambers of the internal combustion
engine. In this exemplary embodiment, let it be assumed that these
fuel injectors 12 are common rail piezoelectric fuel injectors.
From a fuel tank 114 via a fuel line 116 and a high-pressure pump
118, fuel is pumped into a high-pressure reservoir 120 (common
rail). This high-pressure reservoir 120 is part of a high-pressure
part 122 of the fuel injection system. From the high-pressure
reservoir 120, in which a pressure of between 200 bar and 2000 bar
typically prevails, the fuel injectors 112 are acted upon by fuel
for the injection.
[0030] As is known from the prior art, the fuel injectors 112 each
have return branches 124, which in this exemplary embodiment are
combined in a low-pressure reservoir 126 in the form of a return
rail. Via a low-pressure outlet 128, fuel is returned from the
low-pressure reservoir 126 to the fuel tank 114.
[0031] The return branches 124 and the low-pressure reservoir 126
thus form components of a low-pressure part 132 of the fuel
injection system 110. Between the low-pressure reservoir 126 and
the low-pressure outlet 128, a pressure maintenance valve 130 is
provided. This pressure maintenance valve 130 is embodied such that
the pressure in the low-pressure reservoir 126 is set to
approximately 10 bar.
[0032] A metering device 134 is moreover provided, which branches
off from the low-pressure reservoir 126 and leads to a metering
device 136 in the form of a metering valve. Still other embodiments
are conceivable, such as a direct connection of the low-pressure
reservoir 126 to the metering device 136, without the interposition
of a metering line 134.
[0033] The metering device 136 is let into an exhaust manifold 138
of an exhaust system 140 of the engine. The metering device 136 is
embodied such that the fuel can be injected from the metering line
134 into the exhaust system 140. The exhaust system 140 in this
exemplary embodiment furthermore has a device 142 for posttreating
the exhaust gases in the exhaust system 140; it is embodied here as
a particle filter. The fuel injected via the metering device 136
causes soot to burn off in the particle filter 142 and thus brings
about regeneration of this particle filter.
[0034] The fuel injection system of the invention in the embodiment
shown in FIG. 1 furthermore has a pressure measurement system 144,
in the form of a pressure sensor, which furnishes information about
the pressure in the low-pressure part 132 to a control unit 146.
The control unit 146, via a control line 148, controls the metering
behavior of the metering device 136, and in particular the opening
and closing of a metering valve of the metering device 136. In this
way, regeneration of the particle filter 142 can take place, for
instance at regular intervals.
* * * * *